In recent years, along with the discovery and development of organic semiconductor materials, an organic thin film transistor device, in which an organic material instead of an inorganic material is used for carrier transportation, has been prepared, and performance of the device is being promoted gradually. The fundamental structure and function of an Organic Thin Film Transistor (OTFT) are basically the same as those of a traditional Thin Film Transistor (TFT), and the difference lies in that, an organic semiconductor is used by it as the working substance. Regarding a traditional inorganic thin film transistor, it is a field effect transistor of Metal Oxide Semiconductor (MOS) type, and its semiconductor material is usually inorganic silicon. While an organic semiconductor material is used in an organic thin film transistor to replace an inorganic semiconductor material in MOS. As compared with an existing amorphous silicon or polysilicon TFT, an OTFT has the following features. It has low processing temperature, usually below 180° C., so that the energy consumption is decreased significantly, and it is suitable for flexible substrates. In addition, it also has greatly simplified technological process, substantially reduced cost, wide material sources, and big developing potentialities. It is possible for OTFTs to find applications in many electronic products, such as, active matrix displays, smart cards, labels for commodity price and inventory classification, large-area sensor arrays, etc.
As illustrated in FIG. 1, the construction of an organic thin film transistor in prior art includes a base substrate 10, a gate electrode 11 located on the base substrate 10, a gate insulating layer 12 located on the gate electrode 11, a source electrode 13 and a drain electrode 14 that are located on the gate insulating layer 12, and an organic semiconductor active layer 15 located on the source electrode 13 and the drain electrode 14. A photolithography process is usually used for formation of the organic semiconductor active layer 15 in prior art. In the photolithography process, formation of a channel of the organic semiconductor layer is mainly achieved in such a way that the organic semiconductor layer is patterned by using an etching method. But when the channel of the organic semiconductor layer is formed by using an etching method, a photoresist solvent for the etched layer will have an effect on the channel, such as surface dissolution. In addition, channel edges after etch may be affected by an etching media, and for example, edge overetch, oxidation, injection of ions from sidewall or other effect results. In general, such a processing method will affect performance of the channel, and will lead to increasing of a leakage current of the organic thin film transistor.
In summary, when an organic semiconductor layer is patterned by using an etching method in prior art, a photoresist solvent for the etched layer will make an impact on the organic semiconductor layer, leading to degradation in performance of the organic thin film transistor device, and reduction in its service life.